This invention relates to tools and particularly to fastener driving tools having a piston reciprocable in a cylinder under the influence of a pressurized fluid such as pressured air. The piston is movable between an upper rest position and lower driven fastener positions from which it is returnable to the upper rest position until the tool is again actuated to drive another fastener.
Fastener driving tools of this general type are well known. Most of those which are in use are pneumatically operated. Typical tools for driving fasteners such as staples, T-nails and the like are shown in U.S. Pat. Nos. 3,194,324, 3,815,475 and 3,822,819, each of which is owned by the assignee of the present application.
In certain of those patents the use of a rubber or rubber-like bumper is illustrated and described. The function of such a bumper is to engage the piston as it approaches the lower driven fastener position, to cushion its downward movement and to prevent its contacting the nosepiece of the tool or the end of the housing in which the cylinder is positioned.
It will be appreciated that as the tool is used, the bumper will gradually lose its resiliency and will tend to deteriorate and crumble. As that occurs, the travel of the piston will increase, i.e., the initial lower driven fastener position will become lower and lower until the piston approaches and finally contacts the nosepiece or the end of the housing confronting the piston. When the piston contacts the tool nosepiece or end portion of the housing there will be metal-to-metal contact. This will and does result in cracking and destruction of pistons, housings, cylinders, fastener driver blades, i.e., in tool damage and destruction. If metal-to-metal contact continues for relatively few driving cycles, the damage to the tool will require its extensive repair.
However, if the bumper can be maintained to prevent metal-to-metal contact, of course, such extensive tool damage resulting from such contact will be avoided. A means for preventing damage due to such tool-endangering metal-to-metal contact would be highly advantageous.